Many mechanical operations require that one or more workpieces be held stationary for a period of time. Various types of clamps and other devices are known in the art for securing a workpiece in a desired position to facilitate an operation on the workpiece.
An apparatus for securing one or more workpieces is disclosed in U.S. Pat. No. 4,805,888 to Bishop. The Bishop patent describes a two-piece adjustable clamp where the bolt-like portion of each clamp has a lower end threaded into a cooperating tapped hole of a platen, and has an eccentrically-offset upper end about which a shallow nut-like portion is socketed for orbital camming movements. Thus. Bishop's nut-like portion has vertical walls which hold a workpiece laterally when the bolt-like portion is fastened to the platen.
Another apparatus for securely holding a workpiece is described in U.S. Pat. No. 5,310,299 to Bernstein. The Bernstein patent describes a clamping member having a concentric conical bore for receiving a fastener therethrough which when turned engages against the inner bearing surface of the conical bore providing a lateral force which urges the clamping member toward a workpiece and against a stop. However, the clamping surface of Bernstein's clamping member is also vertical.
Accordingly, both clamping devices described by Bishop and Bernstein solely produce a lateral or horizontal force for securing a workpiece against a stop on a platen which is inadequate for securing a workpiece during machining. Consequently, these clamps and other known clamping devices have failed to secure workpieces when a cutting machine is removed from the workpiece. That is, when a cutting machine such as a drill or slitting saw is inserted into the workpiece there is usually no problem as the horizontal or lateral force holds the workpiece; but, when the drill or slitting saw is removed, the workpiece pops or jumps out of the clamp.
Furthermore, in addition to the downtime caused by the workpiece or several workpieces jumping out of the clamp, the jolt which causes the workpieces to pop out also causes damage to the clamp. Thus, considerable time and money are lost in replacing the workpieces and the clamps due to this inferior design.